Eha accumulator refilling arrangement

Abstract

An accumulator assembly for providing hydraulic fluid to an electrohydrostatic actuator includes an accumulator for containing a supply of hydraulic fluid, the accumulator having an exit port via which hydraulic fluid can flow, in use, to the actuator. The assembly further includes an accumulator refill arrangement fluidly connected to a supply of hydraulic fluid for refilling the accumulator via a fluid line when a level of fluid in the accumulator is below a predetermined value. The accumulator includes a cylinder defining a fluid chamber and an accumulator piston moveable within the cylinder relative to the chamber responsive to the fluid pressure. The refill arrangement includes a spool moveable across the fluid line between an open position, wherein fluid can flow along the fluid line from the supply to the chamber, and a closed position, wherein the spool blocks the flow of fluid from the supply to the chamber.

1 . An accumulator assembly for providing hydraulic fluid to an electrohydrostatic actuator, EHA, the assembly comprising:
 an accumulator for containing a supply of hydraulic fluid, the accumulator having an exit port via which hydraulic fluid can flow, in use, to the actuator;   an accumulator refill arrangement fluidly connected to a supply of hydraulic fluid for refilling the accumulator via a fluid line when a level of fluid in the accumulator is below a predetermined value;   wherein the accumulator comprises a cylinder defining a fluid chamber and an accumulator piston moveable within the cylinder relative to the chamber responsive to the fluid pressure;   wherein the refill arrangement includes:
 a spool moveable across the fluid line between an open position; 
 wherein fluid can flow along the fluid line from the supply to the chamber, and a closed position; 
 wherein the spool blocks the flow of fluid from the supply to the chamber and also from the chamber to the supply; and 
 wherein the piston is linked to, and moves, a ramped surface that engages the spool such that the contact force between the ramped surface and the spool varies as the piston moves relative to the chamber, whereby when the chamber is in a full state, the contact force is such as to locate the spool in the closed position and when the level of fluid is less than the predetermined value, the contact force is such as to locate the spool in the open position. 
   
     
     
         2 . The assembly of  claim 1 , wherein the accumulator is a piston and spring type accumulator. 
     
     
         3 . The assembly of  claim 1 , wherein the accumulator is a metal bellows type accumulator. 
     
     
         4 . The assembly of  claim 1 , wherein further comprising:
 a trigger assembly configured to hold the spool in the open position until the level of fluid is equal to or exceeds the predetermined value.   
     
     
         5 . The assembly according to  claim 4 , wherein the trigger assembly comprises:
 a trigger portion of the spool body at an end of the spool body opposite where the spool engages with the ramped surface;   a trigger block configured to engage with the trigger portion of the spool body to prevent the spool body moving to the closed position; and   biasing means arranged to hold the trigger block in engagement with the trigger portion until the level of fluid is equal to or exceeds the predetermined value.   
     
     
         6 . The assembly according to  claim 5 , wherein the trigger block has a tapered surface that, in the open position, engages with the trigger portion of the spool. 
     
     
         7 . The assembly according to  claim 6 , wherein the trigger portion has a tapered surface corresponding to, and engaging with, that of the trigger block. 
     
     
         8 . The assembly of  claim 5 , wherein the biasing means comprises:
 a spool spring biasing the spool in the closed direction and a trigger spring biasing the trigger block into engagement with the trigger portion.   
     
     
         9 . The assembly of  claim 8 , wherein the force of the trigger spring exceeds that of the spool spring, such that the spool spring can only move the spool to the closed position at the end of the stroke of the trigger spring, that occurs when the level of fluid is equal to or exceeds the predetermined value. 
     
     
         10 . An actuator assembly comprising:
 an actuator; and   an accumulator assembly as claimed in claim.   
     
     
         11 . The actuator assembly of  claim 10 , being configured to be mounted on an aircraft wing.